An automobile is provided with a specific key, so that the automobile is prevented from being stolen by operating by a stranger who does not have the specific key.
However, since a conventional automobile operating key serves also as an ignition key, the locking can be released by either of a master key and a duplicated key which coincides with its specific keyway. Moreover, in the case that its key mechanism serves also as an ignition key, an automobile can be started also by direct connection of the wiring.
On the other hand, in recent years, an electronic engine control system using an electronic control unit has increasingly been used for an automobile. The automobile electronic control system has been developed not only for controlling a fuel injection device and an ignition device, but has also been under development into a more comprehensive electronic control system by adding other functions such as an idling speed control, an electronic throttle control, a supercharged pressure control by electronic control, an antilock system, a braking system, a traction control, a self-diagnosis, and further, other functions such as automatic driving, an electronic toll paying function, information collection by connecting to the Internet, and a navigation function using GPS.
The electronic control system comprises sensors arranged at various positions on an automobile, actuators for operating the states of the automobile, and an electronic control unit (ECU). The ECU comprises an input device for receiving outputs from the sensors, a microcomputer, and an output driving part. The microcomputer is comprised of ROM for storing a program incorporating control sequences and logics, EPROM for pre-recording an ignition characteristic map or the like to be used for control, RAM for storing data to be updated as necessary, and an arithmetic operation unit.
Nowadays, an automobile using an electronic control system cannot move at all without operation of the control system.
For some of the automobiles using such an electronic control unit, a car drive disable device (immobilizer) by the electronic control unit is adopted. The immobilizer is automatically activated after turning off an ignition switch to disable at least one of the devices essential to driving the vehicle such as a starter motor circuit, a fuel supply circuit, and an ignition circuit from operating. The circuits for driving the devices are activated by inserting a specific electronic key or inputting a predetermined code through a code keypad.
A conventional immobilizer releases a drive disable state of the car by the same manner, because the immobilizer manages operation of a driving circuit which is completely built in an automobile control device. Therefore, for example, if stealing the cipher code, even a stranger can easily unlock the state.